stackruntime: Pass the apply-time variable values to stackeval

This seems to have got lost while resolving some conflicts in
88eec94.

Without this, apply-time input variable values just get ignored entirely
and if any are required the plan is not applyable at all. Now we'll pass
through what the caller provided so stackeval can validate and use it
properly.

internal/stacks/stackruntime/apply.go

@@ -60,8 +60,9 @@ func Apply(ctx context.Context, req *ApplyRequest, resp *ApplyResponse) {
 		req.Config,
 		req.RawPlan,
 		stackeval.ApplyOpts{
-			ProviderFactories:  req.ProviderFactories,
-			ExperimentsAllowed: req.ExperimentsAllowed,
+			InputVariableValues: req.InputValues,
+			ProviderFactories:   req.ProviderFactories,
+			ExperimentsAllowed:  req.ExperimentsAllowed,
 		},
 		outp,
 	)